Continuous trinitrotoluene manufacture



May 15, 1962 E. SAMUELSEN 3,034,867

CONTINUOUS TRINITROTQLUENE MANUFACTURE Filed Feb. 7, 1956 2 Sheets-Sheet 1 E. SAMUELSEN CONTINUOUS TRINITROTOLUENE MANUFACTURE May 15, 1962 2Sheets-Sheet 2 Filed Feb. '7, 1956 3,934,857 Patented May 15, 19623,034,867 CONTINUOUS TRINITROTOLUENE MANUFACTURE Eirik Samuelsen,Gullaug, Norway, assignor to Aktiebolaget Chematur, Stockholm, Sweden, acorporation of Sweden, and Norsk Spraengstoiindustri A/ S, Oslo,

Norway, a corporation of Norway Filed Feb. 7, 1956, Ser. No. 564,973Claims priority, application Sweden Mar. 23, 1955 Claims. (Cl. 23-266)This invention relates to the nitration of toluene and nitrotoluenes,and particularly to the manufacture of trinitrotoluene by continuousoperation.

It has heretofore been proposed to manufacture trinitrotoluene bycontinuous operation in a series of nitrators and separators, asrepresented, for example, by the United States patent to Holley andMott, No. 1,297,170, to Hock, No. 2,475,095, and to Norell, No.2,594,675.

In all of these older proposals the mixture from a reaction vessel ornitrator is continuously fed to a separator in which nitrobody isseparated from acid; the former being fed to the next nitrator in theseries and the latter to a preceding nitrator and so on. In such systemsthe hold-up time in the nitrator will be of the same order for thetoluene or nitrobody as for the nitrating acid.

It has now been found that when the nitrating acid is given a longerhold up time in comparison with the toluene or nitrobody in thenitrators several advantages over older processes are obtained. Thenitration will be more complete in each step and a higher yield oftrinitrotoluene will be obtained. Such a difference in holdup time canbe arrived at simply by returning part of the separated acid to thenitrator.

The object of the present invention is, generally stated, to provide newand improved apparatus for continuous trinitrotoluene manufacture in aseries of nitrators and separators in which the hold-up times of thereaction phases may be chosen at will.

Another object of this invention is the provision of such apparatus bywhich the volume of the separator can be made smaller than usual, thusreducing the quantities of explosives in operation i.e. obtaininggreater safety in operation.

A further object is the provision of an apparatus by which the feed-backis accomplished by gravity.

Other objects will become apparent to those skilled in the art when thefollowing description is read in connection with the accompanyingdrawings.

In accordance with the present invention, generally stated, partiallyseparated emulsions are fed back from the separators to the nitrators,i.e. part of the emulsions introduced into the separators are broughtback to the nitrators after that part of the disperse-phase or nitrobodyhas separated. It is desirable to feed back a quantity amounting atleast to the half part of the total quantity of the saparated products,i.e. nitrobody and acid, which are leaving the separator. Normally thereturn current will be larger, say 5-15 or more times, the summary ofthe saparated products leaving the separator. With a large returncurrent of partly separated emulsion, it is possible to bring down thequantities of unreacted toluene or nitrobody in the reaction productsleaving the separators to negligible amounts. With a large returncurrent only the larger drops or the more easily separated particles inthe emulsion separate and go into the homogenous phase of outgoingnitrobody. The smaller drops or particles in the emulsion, whichnecessarily must have a longer time to separate, are returned to thenitrator to enter into a new mixing operation. The separator can thus bemade smaller and proportioned after the times necessary to separate thedesired part of the emulsions.

The apparatus according to the invention consists of a system ofnitrator-separators, equipped with mixing devices, cooling devices,inlets and outlets for acids, nitrobody etc. as in other continuoustoluene nitrating systems, and with means by which partly separatedemulsion can be fed back to the nitrator. It is preferable to hold thelevel of the nitrobody in the separator above the level in the attachednitrator, to permit the partly separated emulsion to flow to thenitrator by gravity. The transport of emulsion from the nitrator to theseparator can be performed with the help of a pump or the like. It isalso possible to design the nitrator in such a way that a pumping efiectfrom the mixing device is obtained. The suction or the pumping effectfrom a mixing propeller-or turbine can thus be used. The nitrator canalso be made in the form of an U-vessel with propeller or turbine in oneleg. The liquid in the other leg will thus give a higher level to beused for transport of emulsion to the separator.

Referring now to the drawings for an illustrative embodiment of theinvention FIGURE 1 shows a nitrator 1 with attached separator 2. Thenitrator 1 is equipped with mixing propeller 3, driven 'by an electricalmotor 4, cooling coils 5, inlets 6 and 7 for toluene or nitrobodyrespectively nitrating acid. The outlet 8 of the nitrator is connectedto the inlet 9 of the separator. Through inlet 10 supplementary acid canbe introduced. a lattice, sieve or net work 11 to distribute theincoming emulsion. There is also a pipe 12 to withdraw partly separatedemulsion to the pump 13 and back to the nitrator 1 through pipe 14 andinlet 15. The amount of partly separated emulsion can be regulated by avalve 16. Separated nitrobody is continuously overflowing at the liquidlevel of the separator through outlet 17 and separated acid through anoutlet 18 from the bottom of the separator. The nitrator as well as theseparator can be modified in many ways. Instead of using a nitrator ofordinary shape as illustrated in FIG. 1, it can for instance be giventhe shape of an U-pipe as will be described in the following example.The separator can have a conical inlet to get a good distribution of theemulsion Without net work and the like. The outlet 12 for partlyseparated emulsion can have an adjustable prolongation for instance inthe shape of a telescopic tube to make it possible to regulate theoutlet in vertical as well as horizontal directions. The outlet can alsobe arranged in one or more of the sides of the separator. It is possibleto give the separator vessel the form of a parallelepiped or a lyingcylinder with more or less conical ends or of a standing cylinder withtangential inlet for the emulsion.

In FIGURE 2 there is shown a combination of two apparatus units, eachconsisting of nitrator and separator. In a complete apparatus for themanufacture of trinitrotoluene out of toluene at least three apparatusunits are needed, one unit for each step of nitration. Normally 5-8 ormore units are used as the reaction than are easier to control andhigher output is obtained. The principle of a complete series of unitswill however be easily understood already from a combination of twoapparatus units.

The nitrators 1c, 1d are in this case formed as U-tubes with propelleror turbine 30, 3d in one leg 19c, 19d communicating with the other leg2%, 20d through bottom pipe 21c, 21d. At the upper part of the legsthere is an overflow pipe 22c, 22d. With the propeller 3c, 3d infunction the liquid will rise in the leg 20c, 20d thus creatingsufficient liquid level in the separators 2c, 2d to transport partlyseparated emulsion back to the nitrators without an extra pumpingdevice.

Toluene or separated nitrobody from a preceding unit In the separatorthere is K 3 in the apparatus series is continuously introduced in thenitrator through inlet 60 and is reacted with separated acid coming fromseparator 2d through pipe 23d and introduced through inlet 70. Extraacid (supplementary acid) may be added through inlet 10c, 10d. Part ofthe circulating reaction mixture is removed through outlets 8c andconducted to the separator through inlet 9c. The reaction mixture partlyseparates in the separator; the separated nitrobody being led to thenext nitrator 1d through overflow-outlet 17c and inlet 6d of the saidapparatus. The separated acid is led through outlet 18c throughoverflow-pipe 230 to the preceding nitrator, or in the case of nitrator1c being the first one in the unit series, to a spent acid tank or to adenitrator. Partly separated emulsion, the quantity being regulated byvalve 16c, flows back to the nitrator 1c through pipe 120 and 140respectively, and inlet c.

In the nitrator 1d and separator 2d the operation principle is the same.In the case where this unit is the last in the unit series,trinitrotoluene is withdrawn from the separator 2d through outlet 17dand fresh nitrating acid, or the components of nitrating acid,introduced into the nitrator through inlets 7d and 10d. Separated acidis removed from separator 2d through overflow-outlet 18d and conductedthrough pipe line 23d to the nitrator 10.

In a series of units it will be found that feed-back of partly separatedemulsion has special advantages over feed-back of separated components.The whole system will be easier to control as the change of theconditions in one unit will not influence the other units. This iseasily understood from the fact that the streams of separated productsoverflowing from the outlets of the separator are of the same size evenif the proportions of nitrobody and acid, respectively, the hold up timeof the phases are changed in the nitrators.

The hereinbefore described apparatus constituting the claimed subjectmatter of this application is intended for operation in accordance witha new and improved method of operation forming the claimed subjectmatter of my copending application, divided from this application andfiled Sept. 14, 1961, under Serial No. 142,999.

I claim:

1. Apparatus for nitration of toluene and nitrotoluenes in a series ofunits each consisting of reactor and separator, the outlet from thereactor connected with the inlet of the separator, feeding means to feednitrobody and nitrating acid in countercurrent through the system, theseparator having an outlet between the top and bottom thereof for partlyseparated emulsion of nitrobody and acid, and recycling means to returnpartly separated emulsion of nitrobody and acid from said outlet fromthe separator to reactor in at least one unit of the series.

2. Apparatus according to claim 1 for nitration of toluene andnitrotoluenes to trinitrotoluene in a series of units each consisting ofreactor and separator, in each unit the nitrator having a mixing deviceadapted to feed reaction mixture to the separator and partly separatedemulsion from the separator to the reactor.

3. Reactor-separator unit consisting of a reactor, with mixing device,the outlet from the reactor connected with the inlet of the separator,the separator having an outlet near the top, an outlet at the bottomascending to the proximity of the top outlet level, and a third outletbettween the top and the bottom level, this intermediate outletconnected with the reactor, feeding means to feed mixture from thereactor to the separator and mixture from the intermediate outlet of theseparator to the reactor.

4. Apparatus according to claim 3 wherein the mixing device in thereactor is adapted to feed mixture from the reactor to the separator andfrom the intermediate outlet of the separator to the reactor.

5. Apparatus according to claim 3, for nitration of toluene andnitrotoluenes to trinitrotoluene in a series of reactor-separator unitseach consisting of a unit as set forth in claim 3,

References Cited in the file of this patent UNITED STATES PATENTS1,124,496 Maire Jan. 12, 1915 1,241,017 Quartieri Sept. 25, 19171,297,170 I-Iolley et a1 Mar. 11, 1919 1,638,045 Livingston et a1. Aug.9, 1927 2,363,834 Crater June 30, 1942 2,370,558 Mares Feb. 27, 19452,402,180 Papazoni June 18, 1946 2,475,095 Hoek July 5, 1949 2,594,675Norell Apr. 29, 1952 2,729,549 Roman et al. Jan. 3, 19.56 2,761,768Diels et a1. Sept. 4, 1956

1. APPARATUS FOR NITRATION OF TOLUENCE AND NITROTOLUENES IN A SERIES OFUNITS EACH CONSISTING OF REACTOR AND SEPARATOR, THE OUTLET FROM THEREACTOR CONNECTED WITH THE INLET OF THE SEPARATOR, FEEDING MEANS TO FEEDNITROBODY AND NITRATING ACID IN COUNTERCURRENT THROUGH THE SYSTEEM, THESEPARATOR HAVING AN OUTLET BETWEEN THE TOP AND BOTTOM THEREOF FOR PARTLYSEPARATED EMULSION OF NITROBODY AND ACID, AND RECYCLING MEANS TO RETURNPARTLY SEPARATED EMULSION OF NITROBODY AND ACID FROM SAID OUTLET FROMTHE SEPARATOR TO REACTOR IN AT LEAST ONE UNIT OF THE SERIES.